prime.java.java

求简单的某整数范围内的质数之和

import java.io.*;

public class Prime
{
   static boolean isprime(int x)
   {
      int i,x1;
      x1=(int)Math.sqrt(x);
      for(i=2;i<=x1;i++) 
      if(x%i==0) return false;
      return true;
   }
   public static void main(String args[])
   {
      String s;
      int i,n=0,sum=0;
      boolean b=false;
      do{
         try{
            System.out.print("请输入一个正整数：");
            BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
            s=br.readLine();
            n=Integer.parseInt(s);
            for(i=1;i<=n;i++)
            {
            	 
               if(isprime(i)) sum+=i;
               b=false;
            }
         }
         catch(NumberFormatException nfe)
         {
            System.out.println("整数格式输入错误，请重新输入。\n");
            b=true;
         }
         catch(IOException ioe)
         {
            b=false;
         }
      }while(b);
      System.out.println(n+"以内的各质数之和为："+sum);
   }
}